Minerals may be used in pigments in paper coating and filling compositions. For example, kaolinite, the principal constituent of kaolin clay (or kaolinitic clay), is a white clay mineral that imparts brightness, gloss, smoothness, printability, and/or other desirable properties to the surface of coated paper, paperboard, super-calendared paper, and other paper-related products. Minerals may also be used, for instance, in barrier coatings on paper to impart to paper resistance to moisture, moisture vapor, grease, oil, and air, for example. Such coatings are described in, for example, U.S. Pat. Nos. 7,208,039, 7,214,264, and 7,226,005, which are all hereby incorporated by reference in their entirety.
Typical wax coatings on corrugating paper products offer water barrier properties that may surpass other protective coatings used for corrugated containers. However, wax is derived from petroleum distillation by-products, which are becoming less available and more costly. In addition, the inability to easily recycle these one-time-use wax products may be undesirable.
Re-usable plastic containers might be used in place of corrugated paper products for non-durable food packaging. However, recyclable corrugated containers offer economic advantages as compared to re-usable plastic containers due to their ability to be recycled. For example, the used old corrugated containers may be sold for recycling for favorable prices.
In some instances, latex coating used as a wax coating replacement satisfies the sustainability requirements of retailers for recyclable packaging. Latex coatings can impede liquid water absorption and water vapor transmission. However, the application of latex onto paper products requires additional production costs such as off-line or on-line coating, followed by elevated-temperature-drying by air impingement, irradiation, or other drying processes, or a combination thereof. In addition, the cost of latex is substantially greater than wax and thus a disadvantage.
Accordingly, it would be desirable to provide compositions for coating paper-related products that result in improved barrier performance. For example, it would be desirable to provide coating compositions for coating paper, paperboard, or corrugated linerboard, to provide structural integrity and strength under a number of conditions, for instance, under wet or refrigerated conditions.